Centrifugal fan wheel blades and methods for spinning centrifugal fan wheels incorporating said blades

ABSTRACT

The invention relates to a method of locking blower wheel blades in position by spinning rims around the blower wheel blades having ends with protruding tabs which lock into the rim material when it is spun around these blade ends. In addition, the invention relates to the improvement in centrifugal fan wheels which consist of a blower blade having protruding tabs thereon.

United States Patent [1 1 Morris [451 Oct. 29, 1974 CENTRIFUGAL FAN WHEEL BLADES AND METHODS FOR SPINNING CENTRIFUGAL FAN WHEELS INCORPORATING SAID BLADES [75] Inventor:

[73] Assignee: Baltimore Aircoil Company, Inc.,

Jessup, Md.

[22] Filed: Feb. 16, 19 73 [21] Appl. N0.: 333,416

John Henry Morris, Baltimore, Md.

52 U.S.Cl ..416/178,29/l56.8 CF,4l6/l87 [51] int. Cl B23p 15/02 [58] Field of Search 416/178, 180, 184, 187; 29/156.8 CF, 156.8 FC

[56] References Cited UNITED STATES PATENTS 2,293,512 8/1942 Levy 416/178 2,537,805 1/1951 Wilken 416/184 3,165,258 1/1965 Wentling et al. 416/178 3,711,914 l/l973 Baker 29/l56.8 CF

FOREIGN PATENTS OR APPLICATIONS 558,121 2/1957 Italy 416/178 Primary ExaminerEverette A. Powell, Jr. Attorney, Agent, or FirmMichael C. Sudol, Jr.

[5 7 ABSTRACT The invention relates to a method of locking blower wheel blades in position by spinning rims around the blower wheel blades having ends with protruding tabs which lock into the rim material when it is spun around these blade ends. In addition, the invention relates to the improvement in centrifugal fan wheels which consist of a blower blade having protruding tabs thereon.

1 Claim, 16 Drawing Figures CENTRIFUGAL FAN WHEEL BLADES AND METHODS FOR SPINNING CENTRIFUGAL FAN WHEELS INCORPORATING SAID BLADES BACKGROUND OF THE INVENTION Generally, small blower wheels for use in centrifugal fans are commonly assembled by spinning rims onto end blades. These blade ends are locked into position by the rim being wrapped around the blade end and by rim material which is spun into the space between the blades. A description of this assembly method is shown in US. Pat. No. 2,537,805 to C. E. Wilken assigned to The Lau Blower Company of Dayton, Ohio, patented on Jan. 9, 195 l That patent contains a general description of constructing a centrifugal fan wheel and the instant invention relates to an improvement in the process and apparatus described in that US. Pat. No. 2,537,805.

Referring to the Wilken US. Pat. No. 2,537,805 and particularly FlGS. 4, 5, 6, 7, I and 14 of that patent which are reproduced in this application as FIGS. 11 16, the assembly of the blades are loosely fitted into place each with its inwardly extending notch engaged in the corresponding notch of the center disc. End rings 11 are suitably positioned at either end of the blades, and are provided for receiving the outwardly extending blade flanges therein as the blades are progressively stacked in place. This operation is performed with the blades being introduced into proper position within the end rings and in engagement with the notched center disc as the center disc is slowly rotated on the shaft. The end ring I l is provided with an offset shoulder portion 12 and an inwardly projecting flange portion l3 which is adapted to interfit with the projection formed by the overhanging end flange 14. The projections on the ends of the blades thus are received within the end rings and supported loosely on the shoulders 12 with the flanges 14 extending radially outwardly. The number of blades and the peripheral extent of their end flanges is preferably such that they are not in contact with each other but some clearance there between is provided.

In that Wilken patent process, when the blades are properly assembled, the two end plates are compressed toward each other bringing the respective end rings into tight relation therewith.

The fixture is then rotated and a spinning tool is then brought into working relation with the two end rings 1 l to effect the spinning ofthe rings into final gripping and locking relation with the end flanges of the blades. This operation begins by the pressing downward of the inwardly projecting part 15 of the end ring, the spinning tool being brought to bear against this portion of the ring to cause it to turn over and move downwardly toward the outer surface of the blade as shown in present FIG. 12. As this operation is completed, the spinning tool moves radially inwardly and the material of the portion 15 of the end ring is drawn forcibly into contact with the series of blade flanges 14, causing a firm and secure interlocking action. The operation also tightens the outer portion of ring 1 l, drawing the shoulder 12 forcibly up against the overhanging projection at the base of end flanges 14.

The locking action in the Wilken US. Pat. No. 2,537,805 is provided in the following manner. It is found that the spinning operation may be made to develop substantial forces in the material of the end ring tending to draw or work the metal into the gaps provided'between the end flanges of the blades. This results in forming small projections which extend into the gaps l6 and interlock each blade to hold it securely in position in the end rings. The material of the end ring I l is drawn tightly around the outer peripheral surface 17 of the end flanges and in part into the gaps between those flanges, the pressure being such as to cause the material to be drawn or to flow somewhat into the gaps as indicated at 18, thus forming a series of inward projections between each pair of adjacent blades. These projections on the outer periphery of the end ring in conjunction with the gripping action afforded by the U-shaped section of the end ring engaging opposite sides of the flanges serve to firmly retain the blades in assembled relation.

SUMMARY OF THE PRESENT INVENTION The machinery required to spin rim material around the blade ends and force it into the spaces between ends as described in the Background of the Invention Section is normally quite large and expensive because of the forces required to precisely spin the rims into position. Also this method of spinning, as described above, severely cold forms the rim material where the spinning tool contacts the rim which may cause cracks in the rim, and further may damage any protective coatings such as galvanizing on the rim.

The object of this invention is to form small tabs on the blade ends which will lock the blades into the rim when the rim is spun around the blade ends. These tabs on the blades will lock the blade ends tightly in the rim without forcing the rim material between the blade ends as described in the Wilken patent. The spinning force required to form the rim around the blade ends with tabs is considerably less than the forces required to form the rim around the blade end and force material between the adjoining blade tabs as described in the Wilken patent.

The benefits of this invention are that the spinning machinery can be smaller and less expensive because of the reduced forces and also that the amount of cold forming of the rim material is reduced using my invention.

There are several other advantages of my invention. The primary advantage, of course, is to eliminate the time to spin blades into the fan wheel rim assembly and to insure a tightly spun joint.

However, secondary advantages of my invention are numerous. First the use of my invention eliminates most of the damage to the surface of the galvanized metal of the wheel rims. Second, it reduces significantly the force which was required to get a tightly spun joint thus prolongingthe life of the machinery components. Third, it reduces the time which was formerly required to inspect completed fan wheels for blade tightness, the time required to re-spin wheels with loose blades and the time to readjust spinning machinery.

My invention also came about as the result of problems encountered with attempts to spin together blower wheels considerably larger and of heavier gauge than what had been previously done by the Wilken patent processes described earlier.

The machinery purchased to spin these larger blower wheels together by the Wilken patent method was undersized and would break down under the large forces required to spin by the said Wilken method. Also, be-

cause the forces were larger than expected, the purchased machinery did not have the power required to spin both sides at the same time. i

This invention allowed the use of under designed machinery to spin both sides of the blower wheel at the same time, and gave more consistent results. Also because the spinning force was significantly reduced using my invention, the galvanized steel rims retained their coating whereas with the Wilken patent method described earlier, a good amount of the protective coating was lost where the rim was spun.

Other objects and advantages will be apparent from the following description, the drawings and the appended claims.

FIGS. 1, 2 and 3 are respectively a side view, an end view of FIG. 1 and a fragmentary perspective of an individual blade for a blower wheel constructed in accordance with the present invention.

FIGS. 4-7 show four sequential steps in the assembly of the blades and end rings in the spinning operation.

FIG. 8 is a section through the blade on the line 8-8 of FIG. 7 but without the spinning die or the holding jig shown.

FIGS. 9 and 10 are typical rims for centrifugal fan blower wheels of my invention; FIG. 9 being a typical rim and FIG. 10 being a view along line 10-10 of FIG. 9.

FIGS. 11-14 are essentially FIGS. 4-7 of Wilken US Pat. No. 2,537,805 patented on Jan. 9, l95l and reproduced here to show the state of the prior art and which are referred to in the Background of the Invention section.

Finally FIGS. 15 and 16 are respectively a side elevation view of the fixture used for holding the blade in position during the spinning operation and a perspective view of a formed centrifugal fan blower wheel of the double inlet type. (Present FIGS. 15 and 16 are also respectively FIGS. 10 and 14 of Wilken US Pat. No. 2,537,805 patented Jan 9, 1951 and reproduced to better describe the prior art.)

A fan blade for a blower wheel which normally can have thirty to seventy such blades per wheel is shown in FIGS. 1, 2 and 3. The blade 3 and flange end 2 are of typical form for this type fan wheel. The small tabs 1 shown at the top edge of the blade end 2 are an essential part of this invention.

A formed rim as shown in FIGS. 9 and 10 are a typical form for the type of fan wheel made by my invention. A typical blower wheel as shown in perspective in FIG. 16 has two such rims, but this invention can be applied to designs using one rim only, such as a single inlet blower.

The fan blades which can number from thirty to seventy for the type of wheel made by my invention are placed in a jig, not shown, which equally spaces the blades at approximately the final diameter of the finished wheel. As shown in FIG. 4, the rims 8 are positioned in a holding fixture 9 and the fan blades in a jig are positioned so that the blade ends 2 fit into the fan rims 7.

When the blades and rims are positioned in the holding fixture 9, the holding fixture, rim and blades are rotated at a constant speed and the spinning tool 6 applies pressure close to the end of the portion of the rim being formed 8. As pressure is applied by the spinning tool, said spinning tool 6 will progressively form the end of the rim 8 as shown in FIGS. 5, 6 and 7. The spinning tool 6 is constantly repositioned so that it is applying pressure close to the end of the rim being formed. When the blades and rims are joined as shown in FIG. 7, the spinning tool is removed, the rotation is stopped and the assembly is removed from the holding fixture.

Referring again to the drawings which illustrate my improvement invention, a ty ical blade construction is shown in FIGS. 1, 2 and 3 w ere the blade is shown as having a curved working face 5 which is arcuately shaped in a uniform manner over the major portion of the length of the blade. At either end, the wall of the blade is turned over at approximately right angles as shown at 4 forming a laterally extending wall on the convex side of the blade. Beyond the wall 4, the material of the blade is flanged as shown at 2, this flan e being bent upwardly at right angles to the longitu inally extending blade surface, the flange thus projecting radially outwardly of and overhanging the working face of the blade. As shown the flange 1S tangent to one side of the working face 5 at approximately the point 3, and the end wall 4 is thus of varying width of face as clearly appears in FIG. 3. Also the outer periphery of the flange 2 shown generally as a line 11 in FIG. 2 may be either flat or arcuate at about a radius corresponding to the radius of the blower wheel.

At each end of the blade flange 2 there are located short tabs 1 which are merely the ends of the blade flanges bent inward toward the center of the blade face 5 as opposed to being bent outward away from the blade itself. Generally, the ends of the flange 2 are bent or pressed into shape so that they bend inwards of the flange 2 at approximately an acute angle of from about 25 to about 65 with the face of the flange 2. The bending or pressing of the tabs 1 to the required shape can be performed in the punching operation when the entire blades are made or can be done independently by a separate bending operation. Also, generally, the tabs 1 are bent so that each leg of the triangle formed by the tabs 1 is about 5/32 inches lon These tabs 1 located on the blad e flange 2 are pressed into the rim when the rim is spun over the blade flange and locks the blade into proper position. FIG. 8 shows the rim and blades in the locked position.

I have found that protruding tabs 1 at each end of the flange 2 is the preferred way of carrying out my invention, but others skilled in the art may realize that a single tab at only one end of the flange 2 or a tab or V- notch punch out anywhere alongthe outer periphery of the flange 2 can accomplish my invention. It is my intent that these non-preferred methods be included within the scope of my invention.

The forms 0 apparatus and process herein described are illustrations of my invention and should not be construed as limitations thereof.

What is claimed is:

1. In a centrifugal blower wheel having a plurality of separate blades, each of said blades having a flange at the end thereof extending radially of said wheel, said blades being arranged around the periphery of said wheel and a continuous retaining rim secured in position over said flanges and indented in interlocking relation over said flange portion of said blades for holding the blades in ogerative position with said flanges spaced from eac other to form said wheel, the improvement which comtprises having rotruding enerally radial tabs at the anges of the blades whic lock into the rim when said rim is spun around the blade flanges, the protruding tabs being located at the corner of each flange and facing toward the axial center of the centrifugal lower wheel so that the flanges lock into the rim when said rim is spgn around the blade flanges. 

1. In a centrifugal blower wheel having a plurality of separate blades, each of said blades having a flange at the end thereof extending radially of said wheel, said blades being arranged around the periphery of said wheel and a continuous retaining rim secured in position over said flanges and indented in interlocking relation over said flange portion of said blades for holding the blades in operative position with said flanges spaced from each other to form said wheel, the improvement which comprises having protruding generally radial tabs at the flanges of the blades which lock into the rim when said rim is spun around the blade flanges, the protruding tabs being located at the corner of each flange and facing toward the axial center of the centrifugal blower wheel so that the flanges lock into the rim when said rim is spun around the blade flanges. 